Pneumocystis jirovecii pneumonia as an initial manifestation of hyper-IgM syndrome in an infant: A case report

Kim, Danbi; Shin, Ju Ae; Han, Seung Beom; Chung, Nack-Gyun; Jeong, Dae Chul

About 90% of children with HIGM syndrome experience respiratory tract infection, and P. jirovecii has been the most common respiratory pathogen. [9] [10] [11] [12] Especially, 43% of infants diagnosed with X-linked HIGM syndrome before 1 year of age initially presented with PCP. [11] Primary infection of P. jirovecii occurs during infancy and early childhood. [14] More than 80% of children acquire antibodies against P. jirovecii before 2 years of age, and about 20% of them seem to experience asymptomatic infection. [14] Because respiratory symptoms and signs show no significant difference between children who test positive and negative for P. jirovecii and are diagnosed with respiratory tract infection, except for the frequency of apnea, [14] clinical differentiation of P. jirovecii infection from respiratory tract infection due to other causes should be difficult. In particular, PCP is hardly suspected in children with pneumonia who have no evidence of an underlying immunocompromised state. However, pediatricians should consider that PCP can be an initial clinical presentation of PID, [4] [5] [6] and therefore, PCP should be suspected in infants with severe interstitial pneumonia accompanying normal breathing sounds when common viral and bacterial pathogens are not identified, even though the infants may show no evidence of immune deficiency. In addition, underlying PID should be evaluated in infants diagnosed with PCP using recently developed molecular genetic techniques.